I recently had a problem with an Exchange Online tenant. There was an external mail contact which was previously synchronised from Active Directory to Exchange Online. So I had deleted the on-premise active directory mail contact but it still existed in Exchange Online. When I tried to delete the contact it gave the following errror message.


The action ‘Remove-MailContact’, ‘Identity’, can’t be performed on the object ‘Desmond Miles’ because the object is being synchronized from your on-premises organization. This action should be performed on the object in your on-premises organization.


To trouble shoot this issue you can do a couple of things to ensure the external contact does not exist in your on premise Active Directory.

Connect to your Exchange Online Tenant:

$UserCredential = Get-Credential
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential $UserCredential -Authentication Basic -AllowRedirection
Import-PSSession $Session
  1. Perform a custom search in ADUC: Search Syntax : proxyaddresses=SMTP:[email protected]
  2. Search the WAAD Mettaverse
  3. Run this command on the Exchange Onpremise management shell
    remove-mailcontact [email protected]
So if after running all of the above steps you cannot find the external contact which is causing the issues. You do the following.
In Exchange Online Run this command :
get-mailcontact [email protected] | fl

Take note of the attribute value: ExternalDirectoryObjectId
In this example the externaldirectoryobjectid is 2cb3d9c7-cb29-439f-8174-6c80dd9fe6e8
Then connect to Windows Azure Ad via Powershell and run this command:

get-msolcontact -objectid 2cb3d9c7-cb29-439f-8174-6c80dd9fe6e8 | remove-msolcontact


Problem solved. Now run a delta sync on your WAAD server and everything will work fine.





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